Gibbon genome and the fast karyotype evolution of small apes

Gibbons are small arboreal apes that display an accelerated rate of evolutionary chromosomal rearrangement and occupy akey nodeinthe primate phylogeny between OldWorldmonkeys andgreat apes.Herewepresent the assembly andanalysis of a northern white-cheeked gibbon (Nomascus leucogenys) genome. We describe the propensity for a gibbon-specific retrotransposon (LAVA) to insert into chromosome segregation genes and alter transcription by providing a premature termination site, suggesting a possible molecular mechanism for the genome plasticity of the gibbon lineage. We further show that the gibbon genera (Nomascus, Hylobates, Hoolock and Symphalangus) experienced a near-instantaneous radiation 5 million years ago, coincident with major geographical changes in southeast Asia that caused cycles of habitat compression and expansion. Finally,weidentify signatures of positive selection in genes important for forelimb development (TBX5) and connective tissues (COL1A1) that may have been involved in the adaptation of gibbons to their arboreal habitat.